In plasma display panels (PDPs), CRTs, and the like, electromagnetic shielding is highly important for preventing electromagnetic noises. In one technique for electromagnetic shielding, a metal such as gold or silver or a metal oxide such as ITO is used as an electromagnetic shielding material for these apparatus to form a thin conductive layer or mesh pattern by vapor deposition or the like. Such metal layers or metal oxide layers are generally kept being protected with a protective film until use.
However, when general protective films are used, the surfaces of those metal layers or metal oxide layers are apt to be fouled probably because these surfaces are especially active. There have been cases where this fouling impairs the function of electromagnetic shields.